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          <th colspan="3" align="center">Reviewing Berkeley DB log files</th>
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          <td width="20%" align="left"><a accesskey="p" href="debug_runtime.html">Prev</a> </td>
          <th width="60%" align="center">Chapter 3.  Debugging Applications </th>
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    <div class="sect1" lang="en" xml:lang="en">
      <div class="titlepage">
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          <div>
            <h2 class="title" style="clear: both"><a id="debug_printlog"></a>Reviewing Berkeley DB log files</h2>
          </div>
        </div>
      </div>
      <div class="toc">
        <dl>
          <dt>
            <span class="sect2">
              <a href="debug_printlog.html#idm140188019043680">Augmenting the Log for Debugging</a>
            </span>
          </dt>
          <dt>
            <span class="sect2">
              <a href="debug_printlog.html#idm140188019174416">Extracting Committed Transactions and Transaction Status</a>
            </span>
          </dt>
          <dt>
            <span class="sect2">
              <a href="debug_printlog.html#idm140188019059552">Extracting Transaction Histories</a>
            </span>
          </dt>
          <dt>
            <span class="sect2">
              <a href="debug_printlog.html#idm140188019036896">Extracting File Histories</a>
            </span>
          </dt>
          <dt>
            <span class="sect2">
              <a href="debug_printlog.html#idm140188018982176">Extracting Page Histories</a>
            </span>
          </dt>
          <dt>
            <span class="sect2">
              <a href="debug_printlog.html#idm140188018980624">Other log processing tools</a>
            </span>
          </dt>
        </dl>
      </div>
      <p> 
        If you are running with transactions and logging, the
        <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility can be a useful debugging aid. The <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility
        will display the contents of your log files in a human
        readable (and machine-readable) format. 
    </p>
      <p> 
        The <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility will attempt to display any and all log
        files present in a designated db_home directory. For each log
        record, the <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility will display a line of the form: 
    </p>
      <pre class="programlisting">
[22][28]db_big: rec: 43 txnid 80000963 prevlsn [21][10483281]</pre>
      <p> 
        The opening numbers in square brackets are the
        <span class="emphasis"><em>log sequence number</em></span>
        (<span class="emphasis"><em>LSN</em></span>) of the log record being
        displayed. The first number indicates the log file in which
        the record appears, and the second number indicates the offset
        in that file of the record.
    </p>
      <p> 
        The first character string identifies the particular log
        operation being reported. The log records corresponding to
        particular operations are described following. The rest of the
        line consists of name/value pairs.
    </p>
      <p> 
        The rec field indicates the record type (this is used to
        dispatch records in the log to appropriate recovery
        functions). 
    </p>
      <p>
        The txnid field identifies the transaction for which this
        record was written. A txnid of 0 means that the record was
        written outside the context of any transaction. You will see
        these most frequently for checkpoints. 
    </p>
      <p>
        Finally, the prevlsn contains the LSN of the last record
        for this transaction. By following prevlsn fields, you can
        accumulate all the updates for a particular transaction.
        During normal abort processing, this field is used to quickly
        access all the records for a particular transaction. 
    </p>
      <p>
        After the initial line identifying the record type, each
        field of the log record is displayed, one item per line. There
        are several fields that appear in many different records and a
        few fields that appear only in some records.
    </p>
      <p>
        The following table presents each currently written log
        record type with a brief description of the operation it
        describes. Any of these record types may have the string
        "_debug" appended if they were written because
        <a href="../api_reference/C/dbset_flags.html#dbset_flags_DB_TXN_NOT_DURABLE" class="olink">DB_TXN_NOT_DURABLE</a> was specified and the system was
        configured with <a class="link" href="build_unix_conf.html#build_unix_conf.--enable-diagnostic">--enable-diagnostic</a>. 
    </p>
      <div class="informaltable">
        <table border="1" width="80%">
          <colgroup>
            <col />
            <col />
          </colgroup>
          <thead>
            <tr>
              <th>Log Record Type</th>
              <th>Description</th>
            </tr>
          </thead>
          <tbody>
            <tr>
              <td>bam_adj</td>
              <td>Used when we insert/remove an index
                        into/from the page header of a Btree
                        page.</td>
            </tr>
            <tr>
              <td>bam_cadjust</td>
              <td>Keeps track of record counts in a Btree or
                        Recno database.</td>
            </tr>
            <tr>
              <td>bam_cdel</td>
              <td>Used to mark a record on a page as
                        deleted.</td>
            </tr>
            <tr>
              <td>bam_curadj</td>
              <td>Used to adjust a cursor location when a
                        nearby record changes in a Btree
                        database.</td>
            </tr>
            <tr>
              <td>bam_merge</td>
              <td>Used to merge two Btree database pages
                        during compaction.</td>
            </tr>
            <tr>
              <td>bam_pgno</td>
              <td>Used to replace a page number in a Btree
                        record.</td>
            </tr>
            <tr>
              <td>bam_rcuradj</td>
              <td>Used to adjust a cursor location when a
                        nearby record changes in a Recno
                        database.</td>
            </tr>
            <tr>
              <td>bam_relink</td>
              <td>Fix leaf page prev/next chain when a page
                        is removed.</td>
            </tr>
            <tr>
              <td>bam_repl</td>
              <td>Describes a replace operation on a
                        record.</td>
            </tr>
            <tr>
              <td>bam_root</td>
              <td>Describes an assignment of a root
                        page.</td>
            </tr>
            <tr>
              <td>bam_rsplit</td>
              <td>Describes a reverse page split.</td>
            </tr>
            <tr>
              <td>bam_split</td>
              <td>Describes a page split.</td>
            </tr>
            <tr>
              <td>crdel_inmem_create</td>
              <td>Record the creation of an in-memory named
                        database.</td>
            </tr>
            <tr>
              <td>crdel_inmem_remove</td>
              <td>Record the removal of an in-memory named
                        database.</td>
            </tr>
            <tr>
              <td>crdel_inmem_rename</td>
              <td>Record the rename of an in-memory named
                        database.</td>
            </tr>
            <tr>
              <td>crdel_metasub</td>
              <td>Describes the creation of a metadata page
                        for a subdatabase.</td>
            </tr>
            <tr>
              <td>db_addrem</td>
              <td>Add or remove an item from a page of
                        duplicates.</td>
            </tr>
            <tr>
              <td>db_big</td>
              <td>Add an item to an overflow page
                            (<span class="emphasis"><em>overflow pages</em></span>
                        contain items too large to place on the main
                        page)</td>
            </tr>
            <tr>
              <td>db_cksum</td>
              <td>Unable to checksum a page.</td>
            </tr>
            <tr>
              <td>db_debug</td>
              <td>Log debugging message.</td>
            </tr>
            <tr>
              <td>db_noop</td>
              <td>This marks an operation that did nothing
                        but update the LSN on a page.</td>
            </tr>
            <tr>
              <td>db_ovref</td>
              <td>Increment or decrement the reference count
                        for a big item.</td>
            </tr>
            <tr>
              <td>db_pg_alloc</td>
              <td>Indicates we allocated a page to a
                        database.</td>
            </tr>
            <tr>
              <td>db_pg_free</td>
              <td>Indicates we freed a page (freed pages are
                        added to a freelist and reused).</td>
            </tr>
            <tr>
              <td>db_pg_freedata</td>
              <td>Indicates we freed a page that still
                        contained data entries (freed pages are added
                        to a freelist and reused.)</td>
            </tr>
            <tr>
              <td>db_pg_init</td>
              <td>Indicates we reinitialized a page during a
                        truncate.</td>
            </tr>
            <tr>
              <td>db_pg_sort</td>
              <td>Sort the free page list and free pages at
                        the end of the file.</td>
            </tr>
            <tr>
              <td>dbreg_register</td>
              <td>Records an open of a file (mapping the
                        filename to a log-id that is used in
                        subsequent log operations).</td>
            </tr>
            <tr>
              <td>fop_create</td>
              <td>Create a file in the file system.</td>
            </tr>
            <tr>
              <td>fop_file_remove</td>
              <td>Remove a name in the file system.</td>
            </tr>
            <tr>
              <td>fop_remove</td>
              <td>Remove a file in the file system.</td>
            </tr>
            <tr>
              <td>fop_rename</td>
              <td>Rename a file in the file system.</td>
            </tr>
            <tr>
              <td>fop_write</td>
              <td>Write bytes to an object in the file
                        system.</td>
            </tr>
            <tr>
              <td>ham_chgpg</td>
              <td>Used to adjust a cursor location when a
                        Hash page is removed, and its elements are
                        moved to a different Hash page.</td>
            </tr>
            <tr>
              <td>ham_copypage</td>
              <td>Used when we empty a bucket page, but there
                        are overflow pages for the bucket; one needs
                        to be copied back into the actual
                        bucket.</td>
            </tr>
            <tr>
              <td>ham_curadj</td>
              <td>Used to adjust a cursor location when a
                        nearby record changes in a Hash
                        database.</td>
            </tr>
            <tr>
              <td>ham_groupalloc</td>
              <td>Allocate some number of contiguous pages to
                        the Hash database.</td>
            </tr>
            <tr>
              <td>ham_insdel</td>
              <td>Insert/delete an item on a Hash
                        page.</td>
            </tr>
            <tr>
              <td>ham_metagroup</td>
              <td>Update the metadata page to reflect the
                        allocation of a sequence of contiguous
                        pages.</td>
            </tr>
            <tr>
              <td>ham_newpage</td>
              <td>Adds or removes overflow pages from a Hash
                        bucket.</td>
            </tr>
            <tr>
              <td>ham_replace</td>
              <td>Handle updates to records that are on the
                        main page.</td>
            </tr>
            <tr>
              <td>ham_splitdata</td>
              <td>Record the page data for a split.</td>
            </tr>
            <tr>
              <td>heap_addrem</td>
              <td>Add or remove an entry from a Heap
                        database.</td>
            </tr>
            <tr>
              <td>heap_pg_alloc</td>
              <td>Indicates we allocated a page to a Heap
                        database.</td>
            </tr>
            <tr>
              <td>heap_trunc_meta</td>
              <td>Records the truncation of the meta page in
                        a Heap database.</td>
            </tr>
            <tr>
              <td>heap_trunc_page</td>
              <td>Records the truncation of a data page in a
                        Heap database.</td>
            </tr>
            <tr>
              <td>qam_add</td>
              <td>Describes the actual addition of a new
                        record to a Queue.</td>
            </tr>
            <tr>
              <td>qam_del</td>
              <td>Delete a record in a Queue.</td>
            </tr>
            <tr>
              <td>qam_delext</td>
              <td>Delete a record in a Queue with
                        extents.</td>
            </tr>
            <tr>
              <td>qam_incfirst</td>
              <td>Increments the record number that refers to
                        the first record in the database.</td>
            </tr>
            <tr>
              <td>qam_mvptr</td>
              <td>Indicates we changed the reference to
                        either or both of the first and current
                        records in the file.</td>
            </tr>
            <tr>
              <td>txn_child</td>
              <td>Commit a child transaction.</td>
            </tr>
            <tr>
              <td>txn_ckp</td>
              <td>Transaction checkpoint.</td>
            </tr>
            <tr>
              <td>txn_recycle</td>
              <td>Transaction IDs wrapped.</td>
            </tr>
            <tr>
              <td>txn_regop</td>
              <td>Logs a regular (non-child) transaction
                        commit.</td>
            </tr>
            <tr>
              <td>txn_xa_regop</td>
              <td>Logs a prepare message.</td>
            </tr>
          </tbody>
        </table>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm140188019043680"></a>Augmenting the Log for Debugging</h3>
            </div>
          </div>
        </div>
        <p>
            When debugging applications, it is sometimes useful to
            log not only the actual operations that modify pages, but
            also the underlying Berkeley DB functions being executed.
            This form of logging can add significant bulk to your log,
            but can permit debugging application errors that are
            almost impossible to find any other way. To turn on these
            log messages, specify the --enable-debug_rop and
            --enable-debug_wop configuration options when configuring
            Berkeley DB. See <a class="xref" href="build_unix_conf.html" title="Configuring Berkeley DB">Configuring Berkeley DB</a> for more
            information.
        </p>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm140188019174416"></a>Extracting Committed Transactions and Transaction Status</h3>
            </div>
          </div>
        </div>
        <p>
            Sometimes, it is helpful to use the human-readable log
            output to determine which transactions committed and
            aborted. The awk script, commit.awk, (found in the
            db_printlog directory of the Berkeley DB distribution)
            allows you to do just that. The following command, where
            log_output is the output of db_printlog, will display a
            list of the transaction IDs of all committed transactions
            found in the log: 
        </p>
        <pre class="programlisting">awk -f commit.awk log_output</pre>
        <p>
            If you need a complete list of both committed and
            aborted transactions, then the script status.awk will
            produce it. The syntax is as follows: </p>
        <pre class="programlisting">awk -f status.awk log_output</pre>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm140188019059552"></a>Extracting Transaction Histories</h3>
            </div>
          </div>
        </div>
        <p> 
            Another useful debugging aid is to print out the
            complete history of a transaction. The awk script txn.awk
            allows you to do that. The following command line, where
            log_output is the output of the <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility and txnlist
            is a comma-separated list of transaction IDs, will display
            all log records associated with the designated transaction
            ids: 
        </p>
        <pre class="programlisting">awk -f txn.awk TXN=txnlist log_output</pre>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm140188019036896"></a>Extracting File Histories</h3>
            </div>
          </div>
        </div>
        <p> 
            The awk script fileid.awk allows you to extract all log
            records that refer to a designated file. The syntax for
            the fileid.awk script is the following, where log_output
            is the output of db_printlog and fids is a comma-separated
            list of fileids: 
        </p>
        <pre class="programlisting">awk -f fileid.awk PGNO=fids log_output</pre>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm140188018982176"></a>Extracting Page Histories</h3>
            </div>
          </div>
        </div>
        <p>
            The awk script pgno.awk allows you to extract all log
            records that refer to designated page numbers. However,
            because this script will extract records with the
            designated page numbers for all files, it is most useful
            in conjunction with the fileid script. The syntax for the
            pgno.awk script is the following, where log_output is the
            output of db_printlog and pgnolist is a comma-separated
            list of page numbers:
        </p>
        <pre class="programlisting">awk -f pgno.awk PGNO=pgnolist log_output</pre>
      </div>
      <div class="sect2" lang="en" xml:lang="en">
        <div class="titlepage">
          <div>
            <div>
              <h3 class="title"><a id="idm140188018980624"></a>Other log processing tools</h3>
            </div>
          </div>
        </div>
        <p>
            The awk script count.awk prints out the number of log
            records encountered that belonged to some transaction
            (that is, the number of log records excluding those for
            checkpoints and non-transaction-protected operations).
        </p>
        <p> 
            The script range.awk will extract a subset of a log.
            This is useful when the output of <a href="../api_reference/C/db_printlog.html" class="olink">db_printlog</a> utility is too
            large to be reasonably manipulated with an editor or other
            tool. The syntax for range.awk is the following, where
            <span class="bold"><strong>sf</strong></span> and <span class="bold"><strong>so</strong></span> represent the LSN of the
            beginning of the sublog you want to extract, and <span class="bold"><strong>ef</strong></span> and <span class="bold"><strong>eo</strong></span> 
            represent the LSN of the end of the
            sublog you want to extract: 
        </p>
        <pre class="programlisting">    awk -f range.awk START_FILE=sf START_OFFSET=so END_FILE=ef \
    END_OFFSET=eo log_output </pre>
      </div>
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